trapezium

Etymology

Recorded since 1570, learned borrowing from Late Latin trapezium, from Ancient Greek τραπέζιον (trapézion, “irregular quadrilateral”, literally “a little table”), diminutive of τράπεζα (trápeza, “table”). Doublet of trapeze.

noun

1. (geometry, Britain, Australia, New Zealand) A quadrilateral with two sides parallel.
   1. (restrictively) A quadrilateral with two sides parallel and two sides non-parallel.
2. (geometry, US, dated) A four-sided polygon with no parallel sides and no sides equal; a simple convex irregular quadrilateral.
3. (anatomy) The trapezium bone of the wrist.
4. A region on the ventral side of the brain, either just back of the pons Varolii, or, as in man, covered by the posterior extension of its transverse fibers.